The work of W. Ritchie Russell (1903 - 1980) and colleagues is
the basis of all PTA research. Their studies have shaped much
of what we know about PTA today. Russell et al. used subjective
and retrospective estimates of PTA based on the careful questioning
of patients. In 1943, Symonds & Russell set out 2 warnings
regarding this method. In a nutshell, they said beware of: (1)
'islands' of memory; and (2) the oriented amnesic. These warnings
still apply today.
In their words:
'Care is necessary to avoid two sources of error. One arises
from accepting the patient's first memory of his surroundings
as the end-point, when it has in fact been followed by a further
period of clouded consciousness and amnesia. Such 'islands' of
memory are not uncommon and may be followed by further amnesia
for a day or two; it is therefore the beginning of continuous
memory which we prefer as our measurement. The second, though
less common, error is to assume that because a patient is aware
of what is happening around him he will be able to recall this
later. This may lead to underestimation of the duration of post-traumatic
amnesia in a patient who is under observation in the acute stage
of his symptoms.' [p. 7]
The Westmead PTA Scale's operational definition was designed
with these warnings in mind.
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